A variable-displacement vane pump of the state of the art is described in WO 2005/068838 A1. The pump is provided with a pressure control system for controlling the discharge pressure of the lubricant at the pump outlet port. The pressure control system comprises a first control chamber wherein a first plunger is provided being radially movable. The first control chamber is connected via a first pressure conduit with the pump outlet port. The pressure control system also comprises a separate pressure control valve which is realized as a cylinder-piston-element which keeps the delivery pressure of the pressurized lubricant provided at the pump outlet port at a more or less constant level. This is realized by opening and closing an outlet of the control chamber, thereby allowing the control ring to move into a low pumping volume direction or being pushed into a high pumping volume direction. The pressure control system controls the delivery pressure independently of the lubricant temperature.
The pump is also provided with a pumping volume limitation unit which makes it possible to limit the maximum pumping volume while the lubricant is cold. The pumping volume limitation unit comprises an outlet opening in a side wall of the control chamber, whereby the outlet opening and the first plunger are arranged so that the first plunger covers, and thereby closes, the outlet opening in the lower pumping volume position of the control ring. The volume limitation unit outlet opening is connected to atmospheric pressure via an electric valve which is controlled by a central control unit. The central control unit opens the electric valve when the lubricant is cold and closes the valve when the lubricant is warm. The pumping volume limitation unit is relatively complex and not fail-safe.